Practical Enantioselective Synthesis of Endothelin Antagonist S-1255 by Dynamic Resolution of 4-Methoxychromene-3-carboxylic Acid Intermediate
作者:Toshiro Konoike、Ken-ichi Matsumura、Tadahiko Yorifuji、Shoji Shinomoto、Yutaka Ide、Takashi Ohya
DOI:10.1021/jo0261092
日期:2002.11.1
carbon-carbon bond formation between the C4 carbon and the p-anisyl group was accomplished by a conjugate addition-elimination reaction of Grignard reagent 3 to (R)-16 to give 1 having 98% ee. Owing to high efficiencies of functional group transformations, carbon-carbon bond formations, and the dynamic resolution, the synthesis required no chromatographic purification and was amenable to a multikilogram-scale preparation
描述了对映体纯的S-1255(1)(一种有效的口服活性ET(A)受体拮抗剂)的实用多千克级合成方法。利用容易获得的原料和试剂,从2,5-二羟基苯乙酮8开始的整个反应序列在温和的条件下进行,以优异的化学收率(8步,总收率41%)和高对映体纯度(98%)得到1 ee)。合成的关键步骤是关键中间体16的动态拆分。从外消旋体16以结晶形式(1S,2R)获得具有97-99%ee的(R)-甲氧基酸(R)-16,产率为83-84%。 )-(+)-去氧麻黄碱或(+)-辛可宁盐的动态拆分包括同时结晶和原位外消旋。讨论了通过开环的两性离子中间体进行动态拆分的机理。在最后的合成步骤中,通过格氏试剂3与(R)-16的共轭加成-消除反应,在C4碳和对-茴香基之间有效地形成碳-碳键,得到具有98%ee的1。由于高效的官能团转化,碳-碳键形成和动态拆分,该合成方法无需进行色谱纯化,可进行多千克级的制备。通过此过程成功制